/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server.persistence;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.jute.Record;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.KeeperException.Code;
import org.apache.zookeeper.ZooDefs.OpCode;
import org.apache.zookeeper.server.DataTree;
import org.apache.zookeeper.server.DataTree.ProcessTxnResult;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.ZooTrace;
import org.apache.zookeeper.server.persistence.TxnLog.TxnIterator;
import org.apache.zookeeper.txn.CreateSessionTxn;
import org.apache.zookeeper.txn.TxnHeader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This is a helper class above the implementations of txnlog and snapshot
 * classes
 */
public class FileTxnSnapLog {
	/**
	 * This listener helps the external apis calling restore to gather information
	 * while the data is being restored.
	 */
	public interface PlayBackListener {
		void onTxnLoaded(TxnHeader hdr, Record rec);
	}

	private static final Logger LOG = LoggerFactory.getLogger(FileTxnSnapLog.class);
	public final static String version = "version-";
	public final static int VERSION = 2;
	// the direcotry containing the
	// the transaction logs
	File dataDir;
	// the directory containing the
	// the snapshot directory
	File snapDir;

	SnapShot snapLog;

	TxnLog txnLog;

	/**
	 * the constructor which takes the datadir and snapdir.
	 * 
	 * @param dataDir the trasaction directory
	 * @param snapDir the snapshot directory
	 */
	public FileTxnSnapLog(File dataDir, File snapDir) throws IOException {
		this.dataDir = new File(dataDir, version + VERSION);
		this.snapDir = new File(snapDir, version + VERSION);
		if (!this.dataDir.exists()) {
			if (!this.dataDir.mkdirs()) {
				throw new IOException("Unable to create data directory " + this.dataDir);
			}
		}
		if (!this.snapDir.exists()) {
			if (!this.snapDir.mkdirs()) {
				throw new IOException("Unable to create snap directory " + this.snapDir);
			}
		}
		txnLog = new FileTxnLog(this.dataDir);
		snapLog = new FileSnap(this.snapDir);
	}

	/**
	 * append the request to the transaction logs
	 * 
	 * @param si the request to be appended returns true iff something appended, otw
	 *           false
	 * @throws IOException
	 */
	public boolean append(Request si) throws IOException {
		return txnLog.append(si.hdr, si.txn);
	}

	/**
	 * close the transaction log files
	 * 
	 * @throws IOException
	 */
	public void close() throws IOException {
		txnLog.close();
		snapLog.close();
	}

	/**
	 * commit the transaction of logs
	 * 
	 * @throws IOException
	 */
	public void commit() throws IOException {
		txnLog.commit();
	}

	/**
	 * the most recent snapshot in the snapshot directory
	 * 
	 * @return the file that contains the most recent snapshot
	 * @throws IOException
	 */
	public File findMostRecentSnapshot() throws IOException {
		FileSnap snaplog = new FileSnap(snapDir);
		return snaplog.findMostRecentSnapshot();
	}

	/**
	 * the n most recent snapshots
	 * 
	 * @param n the number of recent snapshots
	 * @return the list of n most recent snapshots, with the most recent in front
	 * @throws IOException
	 */
	public List<File> findNRecentSnapshots(int n) throws IOException {
		FileSnap snaplog = new FileSnap(snapDir);
		return snaplog.findNRecentSnapshots(n);
	}

	/**
	 * get the datadir used by this filetxn snap log
	 * 
	 * @return the data dir
	 */
	public File getDataDir() {
		return this.dataDir;
	}

	/**
	 * the last logged zxid on the transaction logs
	 * 
	 * @return the last logged zxid
	 */
	public long getLastLoggedZxid() {
		FileTxnLog txnLog = new FileTxnLog(dataDir);
		return txnLog.getLastLoggedZxid();
	}

	/**
	 * get the snap dir used by this filetxn snap log
	 * 
	 * @return the snap dir
	 */
	public File getSnapDir() {
		return this.snapDir;
	}

	/**
	 * get the snapshot logs that are greater than the given zxid
	 * 
	 * @param zxid the zxid that contains logs greater than zxid
	 * @return
	 */
	public File[] getSnapshotLogs(long zxid) {
		return FileTxnLog.getLogFiles(dataDir.listFiles(), zxid);
	}

	/**
	 * process the transaction on the datatree
	 * 
	 * @param hdr      the hdr of the transaction
	 * @param dt       the datatree to apply transaction to
	 * @param sessions the sessions to be restored
	 * @param txn      the transaction to be applied
	 */
	public void processTransaction(TxnHeader hdr, DataTree dt, Map<Long, Integer> sessions, Record txn)
			throws KeeperException.NoNodeException {
		ProcessTxnResult rc;
		switch (hdr.getType()) {
		case OpCode.createSession:
			sessions.put(hdr.getClientId(), ((CreateSessionTxn) txn).getTimeOut());
			if (LOG.isTraceEnabled()) {
				ZooTrace.logTraceMessage(LOG, ZooTrace.SESSION_TRACE_MASK,
						"playLog --- create session in log: 0x" + Long.toHexString(hdr.getClientId())
								+ " with timeout: " + ((CreateSessionTxn) txn).getTimeOut());
			}
			// give dataTree a chance to sync its lastProcessedZxid
			rc = dt.processTxn(hdr, txn);
			break;
		case OpCode.closeSession:
			sessions.remove(hdr.getClientId());
			if (LOG.isTraceEnabled()) {
				ZooTrace.logTraceMessage(LOG, ZooTrace.SESSION_TRACE_MASK,
						"playLog --- close session in log: 0x" + Long.toHexString(hdr.getClientId()));
			}
			rc = dt.processTxn(hdr, txn);
			break;
		default:
			rc = dt.processTxn(hdr, txn);
		}

		/**
		 * This should never happen. A NONODE can never show up in the transaction logs.
		 * This is more indicative of a corrupt transaction log. Refer ZOOKEEPER-1333
		 * for more info.
		 */
		if (rc.err != Code.OK.intValue()) {
			if (hdr.getType() == OpCode.create && rc.err == Code.NONODE.intValue()) {
				int lastSlash = rc.path.lastIndexOf('/');
				String parentName = rc.path.substring(0, lastSlash);
				LOG.error("Parent {} missing for {}", parentName, rc.path);
				throw new KeeperException.NoNodeException(parentName);
			} else {
				LOG.debug("Ignoring processTxn failure hdr: " + hdr.getType() + " : error: " + rc.err);
			}
		}
	}

	/**
	 * this function restores the server database after reading from the snapshots
	 * and transaction logs
	 * 
	 * @param dt       the datatree to be restored
	 * @param sessions the sessions to be restored
	 * @param listener the playback listener to run on the database restoration
	 * @return the highest zxid restored
	 * @throws IOException
	 */
	public long restore(DataTree dt, Map<Long, Integer> sessions, PlayBackListener listener) throws IOException {
		snapLog.deserialize(dt, sessions);
		FileTxnLog txnLog = new FileTxnLog(dataDir);
		TxnIterator itr = txnLog.read(dt.lastProcessedZxid + 1);
		long highestZxid = dt.lastProcessedZxid;
		TxnHeader hdr;
		while (true) {
			// iterator points to
			// the first valid txn when initialized
			hdr = itr.getHeader();
			if (hdr == null) {
				// empty logs
				return dt.lastProcessedZxid;
			}
			if (hdr.getZxid() < highestZxid && highestZxid != 0) {
				LOG.error(highestZxid + "(higestZxid) > " + hdr.getZxid() + "(next log) for type " + hdr.getType());
			} else {
				highestZxid = hdr.getZxid();
			}
			try {
				processTransaction(hdr, dt, sessions, itr.getTxn());
			} catch (KeeperException.NoNodeException e) {
				throw new IOException(
						"Failed to process transaction type: " + hdr.getType() + " error: " + e.getMessage(), e);
			}
			listener.onTxnLoaded(hdr, itr.getTxn());
			if (!itr.next())
				break;
		}
		return highestZxid;
	}

	/**
	 * roll the transaction logs
	 * 
	 * @throws IOException
	 */
	public void rollLog() throws IOException {
		txnLog.rollLog();
	}

	/**
	 * save the datatree and the sessions into a snapshot
	 * 
	 * @param dataTree             the datatree to be serialized onto disk
	 * @param sessionsWithTimeouts the sesssion timeouts to be serialized onto disk
	 * @throws IOException
	 */
	public void save(DataTree dataTree, ConcurrentHashMap<Long, Integer> sessionsWithTimeouts) throws IOException {
		long lastZxid = dataTree.lastProcessedZxid;
		File snapshotFile = new File(snapDir, Util.makeSnapshotName(lastZxid));
		LOG.info("Snapshotting: 0x{} to {}", Long.toHexString(lastZxid), snapshotFile);
		snapLog.serialize(dataTree, sessionsWithTimeouts, snapshotFile);

	}

	/**
	 * truncate the transaction logs the zxid specified
	 * 
	 * @param zxid the zxid to truncate the logs to
	 * @return true if able to truncate the log, false if not
	 * @throws IOException
	 */
	public boolean truncateLog(long zxid) throws IOException {
		FileTxnLog txnLog = new FileTxnLog(dataDir);
		return txnLog.truncate(zxid);
	}
}
